Substrate processing method and substrate processing apparatus

ABSTRACT

Resists can be removed while metal contamination of wafers, etc. and generation of particles, and growth of oxide films are suppressed.  
     An ozone gas feed system  40  for feeding ozone gas  2  into a processing vessel  10  holding wafers W, and a steam feed means  30  for feeding steam  1  into the processing vessel  10  are provided. An on-off valve  49  inserted in the ozone gas feed pipe  42,  an on-off valve  36  inserted in the steam feed pipe  34  and a switch  48  and an on-off valve  49  of ozone gas generator  41  are connected to CPU  100  which is control means and are controlled by the CPU  100.  Ozone gas  2  is fed into the processing vessel  10  to pressurize the atmosphere surrounding the wafers W, and then steam  1  is fed into the processing vessel  10  while ozone gas  2  is fed into the processing vessel  10,  whereby a resist of the wafers W can be removed with the steam  1  and the ozone  2  while metal corrosion, etc. can be prevented.

CROSS REFERENCE TO RELATED APPLICATIONS

The subject application is related to subject matter disclosed inJapanese Patent Application No. 2000-304375 filed on Oct. 4, 2000 inJapan and Japanese Patent Application No. 2001-41482 field on Feb. 19 towhich the subject application claims priority under Paris Convention andwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a substrate processing method and asubstrate processing apparatus, more specifically, a substrateprocessing method and a substrate processing apparatus for processingsubstrate-to-be-processed, such as semiconductor wafers, LCD glasssubstrates or others, held in an atmosphere sealed processing vesselwith a processing gas, such as ozone, etc., fed into the processingvessel.

2. Related Background Art

Generally in fabricating a semiconductor device, a series of processingsteps of applying a photoresist to a semiconductor wafer, an LCDsubstrate or others (hereinafter called a wafer or others) as asubstrate-to-be-processed, the step of diminishing a circuit pattern byphotolithography, transferring the circuit pattern to a photoresist anddeveloping the circuit pattern, and the step of removing the photoresistfrom the wafer or others is conducted.

One example of the above-described processing will be explained withreference to FIGS. 1A to 1H by means of a case where asubstrate-to-be-processed is a silicon wafer. First, a thick oxide filmOX1 is formed on the surface of a silicon wafer W (hereinafter called awafer W) (the first oxide film forming step: see FIG. 1A). Then, aresist is applied to the surface of the oxide film OX1 to from a resistpattern RP1 (the first resist pattern forming step: see FIG. 1B). Next,an unnecessary portion of the oxide film is etched off with a chemicalliquid, such as DHF (HF/H₂O) or BHF (the first etching step: see FIG.1C). Then, the resist, which is unnecessary, is released with a chemicalliquid (sulfonated water), a mixed liquid of SPM (H₂SO₄/HEO₂) (the firstresist removing step: see FIG. 1D). Next, a thin oxide film OX2 isformed on the surface of the wafer W from which the unnecessary resisthas been removed (the second oxide film forming step: see FIG. 1E). Aresist is again applied to the surface of the oxide film OX2, and aresist pattern RP2 is formed (the second resist pattern forming step:see FIG. 1F). An unnecessary portion of the oxide film is etched offwith a chemical liquid, such as DHF (HF/HEO), BHF or others (the secondetching step: see FIG. 1G). Finally, the resist, which is unnecessary,is released (the second resist removing step: see FIG. 1H).

In a conventional cleaning equipment used as the above-described resistremoving means, generally wafers, etc. are immersed in cleaning tankfilled with a chemical liquid, such as SPM (a mixed liquid ofH₂SO₄/H₂O₂) (sulfonated water) or others to remove the resist films.

However, when sulfonated water is used as the chemical liquid in thefirst resist removing step (see FIG. 1D), sulfuric acid ions remain onthe surface of the wafer W after the resist has been removed, and thereis a risk that the residual sulfuric acid ions may become a cause forparticles and cause contamination. Furthermore, the residual sulfuricacid ions also causes an uneven thickness and poor film quality of thethin oxide film formed in the following second oxide film forming step(see FIG. 1E).

On the other hand, recently, it is required ecologically to removed theresist with a solution of ozone (O₃), whose waste fluid is easy totreat. In this case, the so-called dip cleaning, in which the wafers orwafers or others are immersed in a cleaning tank filled with a solutionof ozone, is used, so that the resist is oxidized with oxygen radicalsin the solution to be decomposed into carbon dioxide, water, etc.

The above-described solution is generally prepared by bubbling anddissolving a high concentration of ozone gas into pure water, and laterthe thus prepared solution is filled in a cleaning tank. It is oftenthat meanwhile ozone in the solution is decomposed, and the solution hasthe ozone concentration decreased, and a sufficient amount of ozonecannot be supplied to the resist surface. High reaction rates cannot beprovided.

Then, in place of the dip cleaning, in which the wafers or others areimmersed in a solution of ozone, it is proposed to use a processing gas,e.g., ozone, and a vapor, e.g., steam, as a solvent to remove the resistfrom the wafers or others. In this cleaning method, a processing gas,e.g., ozone gas is fed to the wafers or others held in a tightly closedprocessing vessel to thereby remove the resist from the wafers orothers. The use of ozone and steam is free from the residual sulfuricacid ions, and accordingly can improve thickness evenness film qualityof the thin film. In this case, ozone is generated by ozone generatingmeans which mixes oxygen (O₂), a base gas as a raw material withnitrogen (N₂) while being discharged.

However, this ozone gas contains nitrogen as described above. As theozone gas is fed, the nitrogen also flows into the processing vessel tocontact the wafers or others. When nitrogen contacts the wafers orothers, the nitrogen reacts with the ozone gas to corrode and etchmetals of aluminum (Al) and tungsten (W) of the wiring portions, causingparticles. This problem of the metal contamination and particlegeneration is the case also with the wafers or others which have notbeen subjected to the wiring step.

The processing with ozone gas containing nitrogen excessively oxidizesthe wafers or others with NO_(x)- or HNO_(x)-based atmospheres(chemicals), and chemical oxide films grow on the surfaces of the wafersor others, possibly causing thickness unevenness and poor film qualityof the thin oxide film.

SUMMARY OF THE INVENTION

The present invention was made in view of the above-described problems,and an object of the present invention is to provide a substrateprocessing method and a substrate processing apparatus which canfacilitate the removal of resists while suppressing the metalcontamination of wafers or others and the generation of particles, andsuppressing the growth of chemical oxide films on the surfaces of thewafers or others.

To achieve the above-described object, the substrate processing methodaccording to the present invention for processing at least asubstrate-to-be-processed held in a processing vessel with a processinggas fed to the substrate-to-be-processed comprises the step of feedingthe processing gas into the processing vessel to pressurize theatmosphere surrounding the substrate-to-be-processed; and the step offeeding solvent vapor into the processing vessel while feeding theprocessing gas. In the present invention, the processing gas can be,e.g., ozone gas, chlorine gas, fluorine gas, and chlorine gas, fluorinegas, hydrogen gas, etc. pre-containing various radicals.

The substrate processing apparatus according to the present inventionfor processing at least a substrate-to-be-processed held in a processingvessel with a process gas fed to the substrate-to-be-processed comprisesa processing gas feed system for feeding the processing gas into theprocessing vessel; a solvent vapor feed system for feeding solvent vaporinto the processing vessel; a central controller for controlling thefeed of the processing gas and the solvent vapor to be fed into theprocessing vessel; a nitrogen feed pipe for feeding nitrogen gas intothe processing vessel; and a nitrogen gas flow rate controller forcontrolling a nitrogen gas flow rate through the nitrogen gas feed pipe.

A substrate processing apparatus for processing at least asubstrate-to-be-processed held in a processing vessel with ozone gas fedto the substrate-to-be-processed comprises an ozone generator forgenerating ozone gas; an ozone gas feed pipe interconnecting the ozonegas generator and the processing vessel; and a steam feed pipe forfeeding steam into the processing vessel, the ozone gas generator beingconnected to a nitrogen gas feed pipe with a nitrogen gas flow ratecontrol valve inserted in and to an oxygen feed pipe for feeding oxygen.

In the substrate processing method and the substrate processingapparatus according to the present invention, before a processing gas isfed to the processing vessel to process the substrate-to-be-processed,the processing gas is fed into the processing vessel to pressurize theatmosphere surrounding the substrates, whereby the atmosphere in theprocessing vessel is replaced by an atmosphere of the processing gaswhile the interior of the processing vessel is pre-pressurized.Accordingly, the risk that the substrate-to-be-processed may contactgases, etc. other than the processing gas is avoided, and metalcontamination and generation of particles can be accordingly prevented.Rates of the reaction between solvent vapor and the processing gas fedsubsequently into the processing vessel are increased to thereby improveefficiency of the processing.

Furthermore, a feed rate of nitrogen gas is controlled to controletching rates of metals suitably to process substrate-to-be-processedwhich are not subjected to wiring steps. Furthermore, a feed rate ofnitrogen gas is controlled to control growth of an oxide film formed onthe surfaces of substrate-to-be-processed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic sectional view of a substrate-to-be-processedin the first oxide film forming step of the conventional waferprocessing method, which explains one example of the method.

FIG. 1B is a diagrammatic sectional view of thesubstrate-to-be-processed in the first resist pattern forming step ofthe conventional wafer processing method, which shows one example of themethod.

FIG. 1C is a diagrammatic sectional view of thesubstrate-to-be-processed in the first etching step of the conventionalwafer processing method, which shows one example of the method.

FIG. 1D is a diagrammatic sectional view of thesubstrate-to-be-processed in the first resist removing step of theconventional wafer processing method, which shows one example of themethod.

FIG. 1E is a diagrammatic sectional view of thesubstrate-to-be-processed in the second oxide film forming step of theconventional substrate processing method, which explains one example ofthe method.

FIG. 1F is a diagrammatic sectional view of thesubstrate-to-be-processed in the second resist pattern forming step ofthe conventional wafer processing method, which explains one example ofthe method.

FIG. 1G is a diagrammatic sectional view of thesubstrate-to-be-processed in the second etching step of the conventionalsubstrate processing method, which explain one example of the method.

FIG. 1H is a diagrammatic sectional view of thesubstrate-to-be-processed in the second resist removing step of theconventional substrate processing method, which explains one example ofthe method.

FIG. 2 is a diagrammatic sectional view of the substrate processingapparatus according to a first embodiment of the present invention.

FIG. 3 is a sectional view of a major part of the substrate processingapparatus according to the first embodiment in a state where steam andozone gas are fed to wafers in the processing vessel.

FIG. 4 is a perspective view of a wafer guide of the present invention.

FIG. 5 is a diagrammatic sectional view of the substrate processingapparatus according to the first embodiment in a state where hot air isfed to the wafers in the processing vessel.

FIG. 6 is a diagrammatic sectional view of the substrate processingapparatus according to the first embodiment in a state where ozone gasis fed to the wafers in the processing vessel.

FIG. 7 is a diagrammatic sectional view of the wafer processingapparatus in a state where oxygen gas is fed to the wafers in theprocessing vessel.

FIG. 8 is a diagrammatic sectional view of the wafer processingapparatus in a state where an atmosphere in the processing vessel isexhausted.

FIG. 9 is a sectional view of a major part of the wafer processingapparatus according to a second embodiment of the present invention ofthe present invention.

FIG. 10 is a graph of etching rates of aluminum (Al), copper (Cu) andtungsten (W) in a case where ozone gas contains nitrogen (N₂) gas and acase where ozone gas contains no nitrogen (N₂) gas.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention according to a first embodiment of the present inventionwill be explained with reference to the drawings attached hereto. In thepresent embodiment, a resist is removed form a semiconductor wafer W(hereinafter called a wafer W) by using ozone gas.

FIG. 2 is a diagrammatic sectional view of the substrate processingapparatus according to the present embodiment. FIG. 3 is a sectionalview of a major part of the substrate processing apparatus according tothe present embodiment.

The substrate processing apparatus comprises a processing vessel 10 forprocessing a wafer W; a wafer guide 20 as holding means for holding thewafer in the processing vessel 10; steam feed means 30 which is solventsteam feed means (a solvent steam feed system) for feeding steam 1 as asolvent into the processing vessel 10; ozone gas feed means (an ozonegas feed system) 40 which is processing gas feed means for feeding aprocessing gas, e.g., ozone (O₃) gas 2 into the processing vessel 10;interior exhaust means (an interior exhaust system) 50 for dischargingan interior atmosphere in the processing vessel 10; periphery exhaustmeans 60 (for discharging a peripheral atmosphere around the processingvessel 10); air feed means 70 for feeding hot air into the processingvessel 10; an ozone killer 80 as a post-treatment mechanism for removingozone from the interior atmosphere discharged from the interior of theprocessing vessel 10; and exhaust means 90 for discharging an atmospherein the processing vessel 10.

The processing vessel 10 comprises mainly the vessel body 11 of a sizewhich can accommodate a plurality of sheets of wafers, e.g., 50 sheetsof wafers, a vessel cover 12 for closing and opening a loading/unloadingopening 14 formed in the upper end of the vessel body 11, and a vesselbottom 13 for closing an opening in the lower end of the vessel body 11.

The vessel cover 12 has, e.g., reversed U-shaped cross section and canbe moved up and down by a lift mechanism 15. The lift mechanism 15 isconnected to control means, e.g., a central computing unit (centralcontroller) 100 (hereinafter called a CPU 100). The lift mechanism 15 isoperated in response to a control signal from the CPU 100 to open orclose the vessel cover 12. When the vessel cover 12 is lifted, theloading/unloading opening 14 is opened, and the wafers W can be loadedinto the vessel body 11. The vessel cover 12 is lowered after the wafersW have been loaded into the vessel body 11, and the loading/unloadingopening 14 is closed with a gap between the vessel body 11 and thevessel cover 12 tightly sealed with an expandable seal member 16 whichis expanded with injected air. A gap between the vessel body 11 and avessel bottom 13 is tightly sealed with a gasket 17. Thus, a tightlysealed atmosphere is established in the processing vessel 10, and no gascan leak outside.

As opening/closure detecting means for detecting opening/closure of thevessel cover 12, a weight sensor 18 is provided on the upper end of thevessel body 11. The weight sensor 18 detects a weight applied to theupper end of the vessel body 11 when the vessel cover 12 closes theloading/unloading opening 14. A detected signal of the weight sensor 11is supplied to the CPU 100 as control means, and the CPU 100 confirmsopening/closure of the vessel cover 12. For example, when the weightsensor 18 detects a prescribed weight, it is recognized that the vesselcover 12 has been perfectly closed.

A rubber heater 19 a is mounted on the outside surface of the vesselbody 11, and a rubber heater 19 b is mounted on the outside surface ofthe vessel cover 12. A rubber heater 19 c is mounted on the outsidesurface of a vessel bottom 13. The rubber heaters 19 a, 19 b, 19 c areconnected to electric power sources (not shown) and are heated byelectric power supply from the electric power sources so that aninterior atmosphere in the processing vessel 10 can be heated to arequired temperature (within a range of, e.g., 80 to 120° C.). Therubber heaters 19 a, 19 b, 19 c prevent dewing of the vessel body 11.

As shown in FIG. 4, the wafer guide 20 comprises mainly a guide 21, and3 holding members 22 a, 22 b, 22 c which are secured to the guide 21 inparallel with each other. Grooves 23 for holding the wafers W verticallyat the lower peripheral edges are formed in the respective holdingmembers 22 a, 22 b, 22 c at a certain pitch. Accordingly, the waferguide 20 can carry 50 sheets of wafers W (for two wafer carriers),spaced equidistantly from each other. The wafer guide 20 has a shaft 24connected to the guide 21, and the shaft 24 is passed slidably through athrough-hole 12 formed in the upper side of the vessel cover 12. A sealmember 25 which is expandable with injected air is disposed between thethrough-hole 12 a and the shaft 24 so as to make the interior of theprocessing vessel 10 air- and water-tight.

The steam feed means 30 comprises mainly a pure water feed pipe 32connected to a pure water supply source 31; a steam generator 33 forevaporating pure water fed through the pure water feed pipe 32 togenerate steam 1; a steam feed pipe 34 for feeding the steam 1 in thesteam generator 33; and a steam nozzle 35 for injecting the steam fedthrough the steam feed pipe 34 into the processing vessel 10.

The pure water feed pipe 32 has one end connected to the pure watersupply source 31. An on-off valve 36 and a flow rate controller 37 areinserted in the pure water feed pipe 32 in the described order from thepure water supply source 31. The on-off valve 36 and the flow ratecontroller 37 are controlled in response to control signals from the CPU100. That is, the on-off valve 36 is controlled to open or close toadmit or not to admit the pure water to flow. The flow rate controller37 is controlled to have an opening suitable for a flow rate of the purewater. A heater (not shown) is disposed inside the steam generator 33.The pure water fed into the stem generator 33 is evaporated by heat ofthe heater into steam 1. The steam generator 33 is connected to adischarge pipe 111 connected to a mist trap 110 which will be descriedlater. The discharge pipe 111 discharges pure water which has not beenevaporated in the steam generator 33 to the mist trap 110 or the steam 1is discharged to the mist trap 110 until a temperature of the steamgenerator 33 and steam injection are stabilized.

The ozone feed means 40 comprises mainly ozone gas generating means (anozone gas generator) 41; an ozone gas feed pipe 42 for feeding ozone gas2 from the ozone gas generating means 41; and an ozone gas nozzle 43 forinjecting the ozone gas 2 fed through the ozone gas feed pipe 42 into anozone processing chamber 10 a of the processing vessel 10.

The ozone generator 41 generates ozone gas (O₃) by passing oxygen (O₂)as a base gas to be a raw material between discharge electrodes 45, 46which are connected to a high-frequency electric power source 44 whichsupplies a high-frequency voltage.

A switch 47 is inserted in an electric circuit 47 interconnecting thehigh-frequency electric power source 44, and the discharge electrodes45, 46. The switch 48 is controlled in response to a control signal fromthe CPU 100. That is, the switch 48 is controlled based on whether ornot ozone gas to be generated. An on-off valve 49 is inserted in theozone feed pipe 42 on the side of the ozone gas generating means 41. Theon-off valve 49 is controlled in response to a control signal from theCPU 100. That is, the on-off valve 49 is controlled to open or close toadmit or not to admit the ozone gas to flow.

The air feed means 70 comprises mainly an air feed pipe 71 for feedingair; a hot air generator 72 for heating the air fed through the air feedpipe 71 to generate hot air 3; a hot air feed pipe 73 for feeding thehot air 3 generated in the hot air generator 72, a pair of air nozzles74 for discharging the hot air 3 fed through the hot air feed pipe 73.

The air feed pipe 71 has one end connected to an air supply source 75.An on-off valve 76 and a flow rate controller 77 are inserted in the airfeed pipe 71 in the described order from the air supply source 75. Theon-off valve 76 and the flow rate controller 77 are connected to the CPU100, which is the control means. In response to control signals from theCPU 100, whether the air to be fed, and a flow rate of the air arecontrolled. A heater 82 for heating the air is disposed in the hot airgenerator 72. The hot air feed pipe 73 is connected to an air inlet pipe85 which releases the air into an exhaust manifold 83 which will bedescribed later. An on-off valve 86 is inserted in the air inlet pipe85. The on-off valve 86 is controlled by the CPU 100, which is thecontrol means.

The interior exhaust means (interior exhaust system) 50 comprises mainlyan exhaust portion 51 installed in the processing vessel 10; a firstinterior exhaust pipe 52 for exhausting an interior atmosphere in theprocessing vessel 10; a cooling unit 53 connected to the first interiorexhaust pipe 52; a mist trap 110 including a liquid pool 3A connected tothe cooling unit 53 at the downstream thereof; and a second interiorexhaust pipe 54 connected to the mist trap 110 at the upstream thereof.

The exhaust portion 51 takes in an interior atmosphere in the processingvessel 10. The exhaust portion 51 is connected to the first interiorexhaust pipe 52. A bypass pipe 55 is branched from the first interiorexhaust pipe 52, and a forced exhaust mechanism 56 having an ejectormechanism is inserted in the bypass pipe 55. The forced exhaustmechanism 56 is connected to the CPU 100, which is the control means,(the forced exhaust mechanism 56 and the CPU 100 constitute “an exhaustrate adjusting system”) to be operationally controlled by the CPU 100.

The cooling unit 53 cools and condenses the steam 1 discharged from thesteam generator 33 and the steam 1 discharged from the processing vessel10. The exhaust pipe 111 and the first interior exhaust pipe 52 arepassed through the cooling unit 53, and a cooling water feed pipe 57 forfeeding cooling water and a cooling water exhaust pipe 58 fordischarging the cooling water are connected to the cooling unit 53. Flowrate adjusting valves 59 a, 59 b are inserted respectively in thecooling water feed pipe 57 and the cooling water discharge pipe 58 so asto adjust a feeding flow rate and a discharge rate of the cooling water.

The mist trap 110 separates gas and liquid to discharge them. That is,the exhaust portion 51 discharges the steam 1 and the ozone gas 2 in theprocessing vessel 10 to the mist trap 110 through the first interiorexhaust pipe 52. The cooling unit 53 is supplied with cooling waterthrough the cooling water feed pipe 57, and the steam 1 discharged outof the processing vessel 10 is cooled to be condensed while being passedthrough the cooling unit 53. Liquid drops of the steam 1 which has beencondensed and liquefied are dropped into the liquid pool 53A of the misttrap 110. On the other hand, the ozone gas 2 is introduced as it is intothe mist trap 110. The interior atmosphere thus discharged out of theprocessing vessel 10 is separated into the ozone gas 2 and the liquiddrops. The separated ozone gas 2 is discharged into the second interiorexhaust pipe 54 while the liquid drops are discharged into a secondliquid drain pipe 93. The steam 1 and the pure water discharged out ofthe steam generator 33 is introduced into the mist trap 110 through adischarge pipe 111. The pure water flows as it is through the dischargepipe 111. The steam 1 is cooled to be condensed while being passedthrough the cooling unit 53, to be dropped in liquid drops into the misttrap 110.

A first concentration sensor 81 as concentration detecting means fordetecting an ozone concentration in the discharged interior atmosphere,and a ozone killer 80 are inserted in the second interior exhaust pipe54, and the exit of the second interior exhaust pipe 54 is connected toan exhaust manifold 83.

The first concentration sensor 81 in the second interior exhaust pipe 54is positioned upstream of the ozone killer 80. The first concentrationsensor 81 detects an ozone concentration of the discharged interioratmosphere before the discharged interior atmosphere flows into theozone killer 80, so as to detect an ozone concentration in theprocessing vessel 10. The first concentration sensor 81 is connected tothe CPU 100, which is the controller. A detected signal of the firstconcentration sensor 81 is supplied to the CPU 100, and the CPU 100controls the opening and closure of the vessel cover 12, based on anozone concentration detected by the first concentration sensor 81. Thecontrol of the opening/closure of the vessel cover 12 is so set that thevessel cover 12 is not opened, e.g., unless an ozone concentration inthe processing vessel 10 is below a preset value (e.g., 0.1 ppm which isharmless to the human body). Such consideration is made for safety.

The ozone killer 80 thermally decomposes the ozone by heating intooxygen. A heating temperature of the ozone killer 80 is set at, e.g.,above 400° C. Preferably, the ozone killer 80 is connected to aninterruptible power supply (not shown) for stable electric power supplyeven in a power failure, so that the ozone killer 80 can be operatedeven in a power failure to remove the ozone for the safety.

The ozone killer 80 has a temperature sensor 84 as operation detectingmeans for detecting an operational state of the ozone killer 80. Thetemperature sensor 84 detects a heating temperature of the ozone killer90. The temperature sensor 84 is connected to the CPU 100, which is thecontroller. A detected signal of the temperature sensor 84 is suppliedto the CPU 100, and, based on the detected signal, the CPU 100 judgeswhether or not the ozone killer 80 is sufficiently ready for removingthe ozone.

The exhaust manifold 83 collects exhausts of the apparatus. That is, theexhaust manifold 83 is connected to the second interior exhaust pipe 54,the air inlet pipe 85 and a first periphery exhaust pipe 61 which willbe described alter. A plurality of pipes (not shown) behind theprocessing apparatus for taking in an atmosphere are provided for theprevention of diffusion of the ozone gas 2 out of the processingapparatus. The exhaust manifold 83 is connected to an acid exhaust foracid only in the plant to function as a junction of the various exhaustsbefore they are sent to the acid exhaust for acid only.

A second concentration sensor 82 for detecting an ozone concentration isdisposed in the exhaust manifold 83. The second concentration sensor 82disposed in the exhaust manifold 83 is connected to the CPU 10, which isthe controller. A detected signal of the second concentration sensor 82is supplied to the CPU 100, and, based on an ozone concentrationdetected by the second concentration sensor 82, the CPU 100 recognizesthe ozone removing ability of the ozone killer 80 so as to monitorleakage of the ozone gas due to malfunctions of, e.g., the ozone killer80.

The peripheral exhaust means 60 comprises mainly a case 62 covering theprocessing vessel 10; a first peripheral exhaust pipe 61 having one endconnected to a lower part of the case 62 and the other end connected tothe exhaust manifold 83; and a second peripheral exhaust pipe 63 havingone end connected to a lower part of the case 62 and the other endconnected to the first interior exhaust pipe 52.

In the case 62, clean air is fed in a down flow from above to prevent aninterior atmosphere in the case 62, i.e., a peripheral atmosphere aroundthe processing vessel 10 from leaking outside while pushing theperipheral atmosphere downward so that the peripheral atmosphere caneasily enter, the first periphery exhaust pipe 61 and the secondperiphery exhaust pipe 63. A second concentration sensor 66 asperipheral concentration detecting means for detecting an ozoneconcentration of the peripheral atmosphere of the processing vessel 10is disposed in the case 62. The second concentration sensor 66 isconnected to the CPU 100, which is the controller. A detected signal ofthe second concentration sensor 66 is supplied to the CPU 100, and basedon an ozone concentration detected by the second concentration sensor66, the CPU 100 detects leakage of the ozone gas 2.

An on-off valve 64 is inserted in the first periphery exhaust pipe 61.The on-off valve 64 is connected to the CPU 100, which is thecontroller. The CPU 100 opens the on-off valve 64 while the processingis going on in a clean condition. Meanwhile, the first periphery exhaustpipe 61 exhausts the peripheral atmosphere of the processing vessel 10into the exhaust manifold 83.

A periphery forced exhaust mechanism 65 having an ejector mechanism isdisposed in the second periphery exhaust pipe 63. The periphery forcedexhaust mechanism 65 draws the peripheral atmosphere around theprocessing vessel 10 quickly to thereby send the peripheral atmosphereunder pressure to the mist trap 110 for forced exhaust. The peripheralforced exhaust mechanism 65 is connected to the CPU 100, which is thecontroller. The operation of the periphery forced exhaust mechanism 65is controlled in response to a control signal of the CPU 100. While theperipheral forced exhaust mechanism 65 is normally operating, the CPU100 outputs no control signal, and the operation of the peripheralforced exhaust mechanism 65 is stopped.

The exhaust means 90 comprises a first drain pipe 91 connected to thebottom of the processing vessel 10 and to the first interior exhaustpipe 52; and a second liquid drain pipe 93 connected to the bottom ofthe mist trap 110. An on-off valve 92 is inserted in the first liquiddrain pipe 91. An on-off valve 94 is inserted in the second liquid drainpipe 93.

The second liquid drain pipe 93 is communicated with the acid drain foracid only in the plant, because ozone may remain in the liquid.

In the mist trap 110, an emptiness preventing sensor 112, drainage startsensor 113 and a liquid over sensor 114 are arranged in the describedorder from below. Although not shown, the on-off valves 92, 94 and therespective sensors 112, 113, 114 are connected to the CPU 100, which isthe controller. The CPU 100 controls opening and closing of the on-offvalves 92, 94, based on detected signals of the sensors 112, 113, 114.That is, when liquid drops are stored to some extent in the mist trap110, and the liquid surface is detected by the drainage start sensor113, a detected signal of the drainage start sensor 113 is supplied tothe CPU 100. In response to a control signal of the CPU 100, the on-offvalve 94 is opened, and the drainage is started. A liquid surface heightarrives at the liquid over sensor 114, an alarm signal of the liquidover sensor 114 is inputted to the CPU 100. Contrarily, when a liquidsurface is below the emptiness preventing sensor 112, a prohibitionsignal of the emptiness preventing sensor 112 is inputted to the CPU100. In response to the control signal of the CPU 100, the on-off valve94 is closed. The emptiness preventing sensor 112 can prevent the misttrap from being empty as a result all liquid drops flow out of the misttrap 110, and prevent the ozone gas 2 from leaking into the acid exhaustfor acid only in the plant.

Next, the operation of the substrate processing apparatus according tothe prevent invention will be explained with reference to FIG. 3 andFIGS. 5 to 8. A plurality of wafers, e.g., 50 sheets of wafer W whichhave been carried by wafer carrying means (not shown) are transferredonto the wafer guide 20, which is movable upward above the vessel body11 of the processing vessel 10. Then, after the wafer guide 20 has beenlowered, the vessel cover 12 is closed, and the wafers W are held in thetightly closed processing vessel 10.

With the wafers W held in the processing vessel 10, first the on-offvalve 76 of the air feed means 70 is opened while the hot air generator72 is actuated. As shown in FIG. 5, hot air 3 heated up to about 280° C.is fed into the processing vessel 10, and the wafers W and the interioratmosphere of the processing vessel 10 are raised from the normaltemperature (25° C.) to a required temperature (e.g., 80-90° C.).Preferably, the required temperature is set to be above a dew point of asolvent and below a temperature of solvent vapor, and within a range oftemperatures optimum for processing.

Then, as shown in FIG. 6, the ozone gas generating means 41 as the ozonegas feed means is actuated, and a high-frequency voltage is applied tofed oxygen (O₂) to generate ozone (O₃) gas. The on-off valve 49 isopened to feed the ozone gas 2 into the processing vessel 10, and thewafers W and the atmosphere in the processing vessel 10 arepre-pressurized. The ozone gas 2 of an about 9 vol % (volume percentage)concentration is fed at an about 10 l/min, and a pressure in theprocessing vessel 10 can be 0.01-0.03 MPa, which is higher than anatmospheric pressure (0.1 MPa) adjusted to be zero. Thus, the atmospherein the processing vessel 10 can be of ozone alone. Accordingly, stableoxide films can be formed on the surfaces of the wafers W, and the metalcorrosion can be prevented.

After a required period of time of pre-pressurizing the interior of theprocessing vessel 10, the steam feed means 30 is actuated with the ozonegas generating means 41 set on, to feed steam 1 into the processingvessel 10 together with the ozone gas. With a reaction substanceproduced by the steam 1 (solvent vapor) and the ozone gas (processinggas), the wafers W are processed, i.e., a resist is removed from thewafers W (see FIG. 3). At this time, the pre-pressurization maintains apressure in the processing vessel 10 to be higher by 0.01-0.03 MPa thanthe atmosphere (0.1 MPa) adjusted to be zero, whereby a mixed amount ofozone molecules with respect to water molecules is increased to producea large amount of hydrogen oxide radicals. Accordingly, even when theozone gas generating means 41, in which the ozone gas feed means 40ozonizes hydrogen (O₂) alone by discharging, is used, sufficientprocessing for removing a resist can be performed. Furthermore, theprocessing using ozone can be performed in the atmosphere of hightemperature, which makes the processing ability higher.

After the processing has been performed for a required period of time(e.g., 3-6 minutes) under an internal pressure of the processing vessel10 higher by 0.05 MPa than an atmospheric pressure (0.1 MPa) adjusted tobe zero, although the internal pressure of the processing vessel 10depends on a kind of a resist, the feed of the steam from the steam feedmeans 30 is stopped while the operation of the ozone gas generatingmeans 41 is stopped, and oxygen (O₂) as the base gas alone is fed intothe processing vessel 10, whereby abrupt decrease of the pressure in theprocessing vessel 10 is prevented (see FIG. 7). Accordingly, the steamin the processing vessel 10 is prevented from dewing and staying on thewafers W.

After a required period of time (e.g., 10 minutes) of the oxygen feed,the oxygen feed is stopped, and then the forced exhaust mechanism 56 isactuated to forcedly discharge the steam and ozone residing in theprocessing vessel 10. Thus, the processing is completed (see FIG. 8). Atthis time, the on-off valve 92 is opened to drain liquid staying at thebottom of the processing vessel 10.

Then, the lift mechanism 15 is actuated to lift the vessel cover 12,opening the loading/unloading opening 14 of the vessel body 1. Then, thewafer guide 20 is lifted above the processing vessel 10 to unload thewafers out of the processing vessel 10. Then, the wafers W aretransferred onto the wafer carrying means (not shown) to be carried to acleaning processing unit for cleaning with pure water. In the cleaningprocessing unit, the wafers W have the resist cleaned off in thecleaning processing unit.

Thus, the above-described substrate processing is applicable not only tothe removal of resists and prevention of metal corrosion and particlesof wafers W which are subjected to wiring steps, but also to the removalof resists and prevention of metal corrosion and particles of wafers Wwhich are not subjected to wiring steps.

FIG. 9 is a sectional view of a major part of the substrate processingapparatus according to a second embodiment of the present invention. Inthe first embodiment, for the resist removal of wafers W and preventionof metal corrosion and particles, the ozone gas feed means 40, which isthe processing gas feed means, ozonizes oxygen (O₂) alone bydischarging. In the present embodiment, oxygen (O₂) and nitrogen (N₂)are fed to the ozone gas generating means 41 of the ozone gas feed means40 which is processing gas feed means, whereby the ozonization is mademore efficient, a feed amount of nitrogen is controlled to removeresists, and etching rates of metals can be controlled.

That is, in the present embodiment, a nitrogen gas feed pipe 201 forfeeding nitrogen besides an oxygen feed pipe 200 for feeding oxygen isconnected to an ozone generating means 41A of ozone gas feed means 40which is processing gas feed means. A nitrogen gas flow rate controlvalve 202 inserted in the nitrogen gas feed pipe 201 is connected to aCPU 100 (the nitrogen gas flow rate control valve 202 and the CPU 100constitutes “a nitrogen gas controller”), and the nitrogen gas flow ratecontroller 202 is controlled in response to a control signal of the CPU100 to thereby adjust a content of nitrogen in ozone gas.

Nitrogen as well as oxygen is fed to the ozone gas generating means 41A,whereby oxygen molecules and nitrogen molecules staying on dischargeelectrodes 45, 46 of the ozone generating means 41A are decomposed tothereby improve the ozone generating efficiency. Nitrogen contained inthe ozone gas 2 contacts metals of the wafers W, such as aluminum (Al),tungsten (W), etc., and the metals can be etched. Flow rates of thenitrogen is controlled to thereby control etching rates of metals.Accordingly, the substrate processing according to the presentembodiment is suitable for resist removal and metal etching of wafers Wwhich are not subjected to wiring steps.

In the present embodiment, nitrogen (N₂) is fed to the ozone gasgenerating means 41A to control a flow rate of nitrogen (N₂) in theozone gas. However, as indicated by the two-dot-line in FIG. 9, it ispossible that the nitrogen gas feed pipe 203 is connected to theprocessing vessel 10, and the nitrogen gas flow rate control valve 202Ainserted in the nitrogen gas feed pipe is controlled by the CPU 100,which is the control means, to feed nitrogen (N₂) directly into aprocessing chamber 10 a of the processing vessel 10.

The rest part of the second embodiment is the same as that of the firstembodiment described above, and the same members as those of the firstembodiment are represented by the same reference numbers not to repeattheir explanation.

In the second embodiment described above, a flow rate of nitrogen iscontrolled to remove resists from wafers W and to control etching ratesof metals. It is possible that a flow rate of nitrogen is controlled tosuppress growth of oxide films. That is, the processing method accordingto the present invention is applied to the first resist removing step(see FIG. 1D) of the processing steps shown in FIG. 1, whereby growth ofchemical oxide films on the surfaces of wafers W can be suppressed. Filmthickness evenness and film quality of thin films can be improved.

In the above-described embodiments, the substrate-to-be-processed iswafer W. However, the substrate-to-be-processed is not essentially waferW and may be, e.g., LCD substrate, substrate, as of CD, etc. as long asthe substrate has resists applied to or metal films applied to.

EXAMPLES Example 1

Experiments were made under the following conditions on etching rates ofmetals in the case where ozone gas contains nitrogen (N₂) and in thecase where ozone gas contains no nitrogen (N₂).

Experiment Conditions:

-   A) Specimen metals: aluminum (Al), copper (Cu) and tungsten (W)-   B) Processing conditions:-   1) For the case where ozone gas contains nitrogen (N₂):    -   Pressure: 70.0[kPa]    -   Wafer temperature: 80[°C.]    -   Steam temperature: 115[°C.]    -   Processing period of time: 5 [min]-   2) For the case where ozone gas contains no nitrogen (N₂):    -   Pressure: 70.0[kPa]    -   Wafer temperature: 80[°C.]    -   Steam temperature: 115[°C.]    -   Processing period of time: 5 [min]

The experiments were conducted under the above-described conditions, andthe results of the experiments are as shown in FIG. 10.

The aluminum (Al) specimen had an etching rate of 86.38 [angstrom/min]in the case where ozone gas contained nitrogen (N₂), and in the casewhere ozone gas alone was used, the aluminum (Al) specimen was notalmost etched, and an etching rate was −1.06 [angstrom/min]. The copper(Cu) specimen had an etching rate of above 100 [angstrom/min] in thecase where ozone gas contained nitrogen (N₂), and in the case whereozone alone was used, the copper (Cu) specimen was 2.28 [angstrom/min].The tungsten (W) specimen had an etching rate of 45.82 [angstrom/min] inthe case where ozone gas contains nitrogen (N₂), and in the case whereozone gas alone was used, the tungsten (W) specimen had an etching rateof 3.32 [angstrom/min].

The results of the experiments described above show that metals, such asaluminum (Al), copper (Cu), tungsten (W), etc., can be etched at largeetching rates when ozone gas contains nitrogen (N₂). By suitablychanging the content of nitrogen (N₂), i.e., conditions of pressure,temperature, etc., etching rates of the above-described metals can becontrolled.

Example 2

Experiments were made under the following conditions on growth rates ofchemical oxide films in cases of resist removal processing using ozonegas having different nitrogen addition amounts (contents).

-   -   Ozone gas: 10 l/min (N₂ added; No N₂ added)    -   Steam: 120° C.    -   Wafer temperature: 90° C.    -   Pressure: 0.05 MPa (Zero-adjusted atmospheric pressure (0.1        MPa))    -   Ozone gas/steam feed period of time: 5 minutes    -   N₂ feed rate: 0.08 l/min

The experiments were made under the above-described conditions, and theresults shown in TABLE 1 were obtained. TABLE 1 Oxide film Oxide filmOxide film thickness thickness growth before processed after processedamount Processed with 3.35 16.90 13.55 ozone gas with [angstrom][angstrom] [angstrom] Nadded processed with 3.70 11.23 7.54 ozone gaswith- [angstrom] [angstrom] [angstrom] out N₂ added

According to the results of the above-described experiments, in the casewhere the resist removing processing was performed with ozone gas (O₃concentration: 10%) with N₂ added, a thickness of an oxide film was 3.35[angstrom] before the processing, and was 16.90 [angstrom] after theprocessing, and a growth amount of the oxide film was 13.55 [angstrom].In contrast to this, in the case where the resist removing processingwas performed with ozone gas (O₃ concentration: 4%) without N₂ added, athickness of an oxide film was 3.70 [angstrom] before the processing andwas 11.23 [angstrom] after the processing, and a growth amount of theoxide film was 7.54 [angstrom].

Accordingly, it is found that the resist removing processing with ozonegas without N₂ added can depress the growth amount of the oxide film by13.55−7.54=6.01 [angstrom] in comparison with the resist removingprocessing with ozone gas with N₂ added.

The thin film OX₂ of FIG. 1E, which is usually formed by, e.g., furnaceprocessing is usually required to have a 10-15 [angstrom]-thickness.However, the processing with ozone gas with N₂ added as described aboveincreases the thickness of the oxide film before processed to 16.90[angstrom], which exceeds the required maximum thickness value 15[angstrom]. However, when the processing with ozone gas without N₂ addedis performed, the oxide film thickness after processed is 11.23[angstrom], which is within the required film thickness range. The thinoxide film after processed can have, by furnace processing, improvedfilm quality (higher density) and even thickness.

In the above-described experiments, N₂ feed amounts were 0.08 l/min and0. However, the growth of an oxide film can be optionally controlled inthe resist removing processing by experimentally obtaining thickness ofan oxide film before and after the resist removing processing, based onN₂ feed amounts other than the above-described N₂ feed amounts,obtaining experimental data of the other conditions, and storing thethus-obtained data in the CPU 100, which is the control means.

As described above, the present invention has the above-describedconstitution, which produces the following effects.

-   -   1) According to the present invention, before a processing gas        is fed to the substrate-to-be-processed in the processing vessel        to process the substrate-to-be-processed, the processing gas is        fed into the processing vessel to pressurize the atmosphere        surrounding the substrates, whereby the atmosphere in the        processing vessel is replaced by an atmosphere of the processing        gas while the interior of the processing vessel is        pre-pressurized. Accordingly, the risk that the        substrate-to-be-processed may contact gases, etc. other than the        processing gas is avoided, and metal contamination and        generation of particles can be accordingly prevented. Rates of        the reaction between solvent vapor and the processing gas fed        into the processing vessel are increased to thereby improve        efficiency of the processing.    -   2) According to the present invention, in the state that the        atmosphere in the processing vessel is replaced by an atmosphere        of a processing gas while pre-pressurizing the interior of the        processing vessel, the substrate-to-be-processed is processed        with solvent steam and the processing gas. Then, the feed of the        solvent vapor is stopped while the generation of the processing        gas is stopped, and a base gas of the processing gas is fed into        the processing vessel, whereby abrupt depressurization in the        processing vessel can be suppressed to prevent the solvent vapor        from dewing. In addition to the effect described above in item        1), liquid drops are prevented from staying on the        substrates-to-be-processed, and yields can be accordingly        increased.    -   3) According to the present invention, in the state that the        atmosphere in the processing vessel is replaced by an atmosphere        of a processing gas while pre-pressurizing the interior of the        processing vessel, the substrate-to-be-processed is processed        with solvent vapor and the processing gas. Then, the feed of the        solvent vapor is stopped while the generation of the processing        gas is stopped, and a base gas of the processing gas is fed into        the processing vessel, whereby abrupt depressurization in the        processing vessel can be suppressed to prevent the solvent vapor        from dewing. Then, the feed of the base gas is stopped, and the        atmospheric gas in the processing vessel can be exhausted. Thus,        in addition to the effects described in items 1) and 2), the        substrate-to-be-processed can be continuously processed with the        solvent vapor and the processing gas without causing metal        contamination to the substrate-to-be-processed and generation of        particles. Consequently, efficiency of the processing can be        improved.    -   4) The interior of the processing vessel is adjusted to have a        required temperature before a processing gas is fed into the        processing vessel, which permits solvent vapor to be fed to the        substrate-to-be-processed after the substrate-to-be-processed        has been heated to the required temperature. In addition to the        effects described in items 1), 2) and 3), a layer of the solvent        molecules can be formed in high density on the surfaces of the        substrate-to-be-processed without failure, and a large amount of        a reaction product can be produced to thereby improve efficiency        of the processing.    -   5) According to the present invention, before a solvent vapor        and ozone gas are fed to the substrate-to-be-processed in the        processing vessel to process the substrate-to-be-processed,        ozone gas is fed into the processing vessel to pressurize the        atmosphere surrounding the substrates, whereby the atmosphere in        the processing vessel is replaced by an atmosphere of ozone gas        while the interior of the processing vessel is pre-pressurized.        Accordingly, the risk that the substrate-to-be-processed may        contact gases, etc. other than ozone gas is avoided, and metal        contamination and generation of particles can be accordingly        prevented. Rates of the reaction between the solvent vapor and        the ozone gas fed into the processing vessel are increased to        thereby improve efficiency of the processing. Furthermore, a        feed rate of nitrogen gas is controlled to control etching rates        of metals suitably to process the substrate-to-be-processed        which is not subjected to wiring steps. Furthermore, a feed rate        of nitrogen gas is controlled to control growth of an oxide film        formed on the surfaces of the substrate-to-be-processed.        Accordingly, whether metal wiring is present or absent,        generation of particles and contamination can be prevented, and        in forming a thin oxide film, evenness of the film thickness and        improved film quality can be achieved.

1: A substrate processing method for processing at least asubstrate-to-be-processed held in a processing vessel with a processinggas fed to the substrate, the method comprising the steps of: feedingthe processing gas into the processing vessel to pressurize theatmosphere surrounding the substrate; and feeding a solvent vapor intothe processing vessel while feeding the processing gas. 2: The substrateprocessing method according to claim 1, further comprising the step of:stopping feeding the solvent vapor while stopping generating theprocessing gas, and feeding a base gas of the processing gas into theprocessing vessel. 3: The substrate processing method according to claim2, further comprising the step of: stopping feeding the base gas whileexhausting a atmospheric gas in the processing vessel. 4: The substrateprocessing method according to claim 1, further comprising the step of:adjusting a temperature of the substrate before the processing gas isfed into the processing vessel. 5: The substrate processing methodaccording to claim 4, wherein in the step of adjusting a temperature ofthe substrate, a gas having a adjusted temperature is fed to thesubstrate. 6: The substrate processing method according to claim 1,wherein the processing gas is ozone gas, and the solvent vapor is steam.7: The substrate processing method according to claim 6, wherein in thestep of feeding ozone gas and steam to process the substrate, nitrogengas is fed into the processing vessel while a feed amount of nitrogengas is adjusted. 8: The substrate processing method according to claim7, wherein the feed amount of nitrogen gas is controlled to be zero. 9:The substrate processing method according to claim 7, wherein thesubstrate is a semiconductor substrate having a metal wiring. 10-17.(canceled)